IMAGING LENS AND IMAGING DEVICE

Abstract

An imaging lens is provided with: a first lens with negative power; a second lens with negative power; a third lens with positive power; and a fourth lens with positive power. The cemented fourth lens is formed from an object side lens with negative power and an image side lens with positive power. The thickness of a resin adhesive layer that bonds the object side lens and the image side lens is 20 m or greater on the optical axis, and when Sg1H is the amount of sag in the image side lens surface of the object side lens and Sg2H is the amount of sag in the object side lens surface of the image side lens. The bonding operation is easy without damage occurring to the cemented surfaces, with a design that takes into account thickness of the resin adhesive layer; therefore various forms of aberration can be corrected.

Claims

1. An imaging device for visible light ray and near infrared ray comprising: a cemented lens composed of a negative lens and a positive lens, and an image pick-up device, wherein the negative lens and the positive lens being cemented together with an adhesive layer; a first cemented surface of the negative lens adjacent the adhesive layer and a second cemented surface of the positive lens adjacent the adhesive layer have different aspheric shapes.

2. The imaging device according to claim 1, wherein the visible light ray has a wavelength of 400 nm to 700 nm, and the near infrared ray has a wavelength of 800 nm to 1100 nm.

3. The imaging device according to claim 1, wherein the image pick-up device is a CCD sensor or a CMOS sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a configuration diagram of an imaging lens of Example 1 to which the present invention is applied.

[0029] FIG. 2 is an explanatory diagram of the amount of sag.

[0030] FIG. 3A is a longitudinal aberration graph of the imaging lens of FIG. 1.

[0031] FIG. 3B is lateral aberration graphs of the imaging lens of FIG. 1.

[0032] FIG. 3C is a field curvature graph of the imaging lens of FIG. 1.

[0033] FIG. 3D is a distortion aberration graph of the imaging lens of FIG. 1.

[0034] FIG. 4 is a spherical aberration graph of the imaging lens of FIG. 1.

[0035] FIG. 5 is a configuration diagram of an imaging lens of Example 2 to which the present invention is applied.

[0036] FIG. 6A is a longitudinal aberration graph of the imaging lens of FIG. 5.

[0037] FIG. 6B is lateral aberration graphs of the imaging lens of FIG. 5.

[0038] FIG. 6C is a field curvature graph of the imaging lens of FIG. 5.

[0039] FIG. 6D is a distortion aberration graph of the imaging lens of FIG. 5.

[0040] FIG. 7 is a spherical aberration graph of the imaging lens of FIG. 5.

[0041] FIG. 8 is a configuration diagram of an imaging lens of Example 3 to which the present invention is applied.

[0042] FIG. 9A is a longitudinal aberration graph of the imaging lens of FIG. 8.

[0043] FIG. 9B is lateral aberration graphs of the imaging lens of FIG. 8.

[0044] FIG. 9C is a field curvature graph of the imaging lens of FIG. 8.

[0045] FIG. 9D is a distortion aberration graph of the imaging lens of FIG. 8.

[0046] FIG. 10 is a spherical aberration graph of the imaging lens of FIG. 8.

[0047] FIG. 11 is a configuration diagram of an imaging lens of Example 4 to which the present invention is applied.

[0048] FIG. 12A is a longitudinal aberration graph of the imaging lens of FIG. 11.

[0049] FIG. 12B is lateral aberration graphs of the imaging lens of FIG. 11.

[0050] FIG. 12C is a field curvature graph of the imaging lens of FIG. 11.

[0051] FIG. 12D is a distortion aberration graph of the imaging lens of FIG. 11.

[0052] FIG. 13 is a spherical aberration graph of the imaging lens of FIG. 11.

[0053] FIG. 14 is a configuration diagram of an imaging lens of Example 5 to which the present invention is applied.

[0054] FIG. 15A is a longitudinal aberration graph of the imaging lens of FIG. 14.

[0055] FIG. 15B is lateral aberration graphs of the imaging lens of FIG. 14.

[0056] FIG. 15C is a field curvature graph of the imaging lens of FIG. 14.

[0057] FIG. 15D is a distortion aberration graph of the imaging lens of FIG. 14.

[0058] FIG. 16 is a spherical aberration graph of the imaging lens of FIG. 14.

[0059] FIG. 17 is an explanatory diagram of an imaging device equipped with an imaging lens.

[0060] FIG. 18 is a configuration diagram of an imaging lens of Reference Example 1.

[0061] FIG. 19A is a longitudinal aberration graph of the imaging lens of FIG. 18.

[0062] FIG. 19B is lateral aberration graphs of the imaging lens of FIG. 18.

[0063] FIG. 19C is a field curvature graph of the imaging lens of FIG. 18.

[0064] FIG. 19D is a distortion aberration graph of the imaging lens of FIG. 18.

[0065] FIG. 20 is a configuration diagram of an imaging lens of Reference Example 2.

[0066] FIG. 21A is a longitudinal aberration graph of the imaging lens of FIG. 20.

[0067] FIG. 21B is lateral aberration graphs of the imaging lens of FIG. 20.

[0068] FIG. 21C is a field curvature graph of the imaging lens of FIG. 20.

[0069] FIG. 21D is a distortion aberration graph of the imaging lens of FIG. 20.

[0070] FIG. 22 is a configuration diagram of an imaging lens of Reference Example 3.

[0071] FIG. 23A is a longitudinal aberration graph of the imaging lens of FIG. 22.

[0072] FIG. 23B is lateral aberration graphs of the imaging lens of FIG. 22.

[0073] FIG. 23C is a field curvature graph of the imaging lens of FIG. 22.

[0074] FIG. 23D is a distortion aberration graph of the imaging lens of FIG. 22.

MODE FOR CARRYING OUT THE INVENTION

[0075] An imaging lens to which the present invention is applied is described below with reference to the drawings.

Example 1

[0076] FIG. 1 is a configuration diagram (light ray diagram) of an imaging lens of Example 1. An imaging lens 10 of the present example comprises, in order from an object side to an image side, a first lens 11 having negative power, a second lens 12 having negative power, a third lens 13 having positive power, and a fourth lens 14 having positive power. A diaphragm 15 is arranged between the third lens 13 and the fourth lens 14, and plate glass 16 is disposed on the image side of the fourth lens 14. An image-forming surface I1 is in a separate position from the plate glass 16. The fourth lens 14 is a cemented lens comprising an object side lens 17 having negative power and an image side lens 18 having positive power. The object side lens 17 and the image side lens 18 are bonded by a resin adhesive, and a resin adhesive layer B1 is formed between the object side lens 17 and the image side lens 18.

[0077] In the first lens 11, an object side lens surface 11a is a meniscus lens protruding toward the object side. The object side lens surface 11a and an image side lens surface 11b of the first lens 11 both have positive curvature.

[0078] In the second lens 12, an object side lens surface 12a has negative curvature, and an image side lens surface 12b has positive curvature. Therefore, the object side lens surface 12a has a concave curved portion that caves to the image side along the optical axis L1, and the image side lens surface 12b has a concave curved portion that caves to the object side along the optical axis L1. The object side lens surface 12a and the image side lens surface 12b are aspheric in shape.

[0079] In the third lens 13, an object side lens surface 13a has positive curvature, and an image side lens surface 13b has positive curvature. Therefore, the object side lens surface 13a has a convex curved portion that protrudes to the object side along the optical axis L1, and the image side lens surface 13b has a convex curved portion that protrudes to the image side along the optical axis L1. The object side lens surface 13a and the image side lens surface 13b of the third lens 13 are aspheric in shape.

[0080] In an object side lens 17 of the fourth lens 14, an object side lens surface 17a has positive curvature, and an image side lens surface 17b has positive curvature. Therefore, the object side lens surface 17a has a convex curved portion that protrudes to the object side along the optical axis L1, and the image side lens surface 17b has a concave curved portion that caves to the object side along the optical axis L1. The object side lens surface 17a and the image side lens surface 17b of the object side lens 17 are aspheric in shape.

[0081] In the image side lens 18 of the fourth lens 14, an object side lens surface 18a has positive curvature, and an image side lens surface 18b has negative curvature. Therefore, the object side lens surface 18a has a convex curved portion that protrudes to the object side along the optical axis L1, and the image side lens surface 18b has a convex curved portion that protrudes to the image side along the optical axis L1. The object side lens surface 18a and the image side lens surface 18b of the image side lens 18 are aspheric in shape.

[0082] The image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18, which constitute the cemented surfaces of the object side lens 17 and the image side lens 18, have different aspheric shapes. When D is the thickness of the resin adhesive layer B1 on the optical axis L1, Sg1H is the amount of sag in the image side lens surface 17b of the object side lens 17 at height H in the effective diameter of the image side lens surface 17b of the object side lens 17 in a direction orthogonal to the optical axis L1, and Sg2H is the amount of sag in the object side lens surface 18a of the image side lens 18 at height H, then the imaging lens 10 of the present example satisfies the conditional expressions (1) and (2) below. The amount of sag is the distance along the optical axis L1 from a reference plane to a lens surface at height H in the effective diameter of the image side lens surface 17b of the object side lens 17 in a direction orthogonal to the optical axis L1, the reference plane being a flat plane orthogonal to the optical axis L1 and including the point of intersection between the lens surface and the optical axis L1. FIG. 2 is an explanatory diagram of the amount of sag, wherein S1 indicates a reference plane relative to the image side lens surface 17b of the object side lens 17, and S2 indicates a reference plane relative to the object side lens surface 18a of the image side lens 18.

20 mD(1)

Sg1HSg2H(2)

[0083] The conditional expressions (1) and (2) stipulate the thickness of the resin adhesive layer B1 between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 which have different aspheric shapes, or in other words, the gap between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18, which are the cemented surfaces of the two lenses constituting the cemented lens.

[0084] Because the imaging lens 10 of the present example satisfies the conditional expressions (1) and (2), the gap between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18 can be enlarged. Therefore, during the bonding operation of bonding the object side lens 17 and the image side lens 18, it is possible to prevent or suppress contact between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18, as well as any damage that may occur on these lens surfaces. Because there is a large gap between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18, the resin adhesive easily fills in between the lens surfaces, and air bubbles can be prevented from remaining in between the two lenses.

[0085] The imaging lens 10 of the present example satisfies the following conditional expression (3).

D100 m(3)

[0086] The purpose of conditional expression (3) is to suppress the increase in the plus-side shift of the field curvature in a tangential surface. When the upper limit of conditional expression (3) is exceeded, the plus-side shift of the field curvature becomes larger and difficult to correct. In the present example, because D is equal to 20 m, the plus-side shift of the field of curvature in the tangential surface can be corrected by the design.

[0087] Furthermore, when Rs is the radius of curvature of the image side lens surface 17b of the object side lens 17 and f is the focal point distance of the entire lens system, the imaging lens 10 of the present example satisfies the following conditional expression (4).

0.9Rs/f1.3(4)

[0088] When Rs/f falls below the lower limit of conditional expression (4), the curvature of the image side lens surface 17b of the object side lens 17 becomes large; therefore, cementing with the image side lens 18 is no longer easy and the work of cementing the cemented lens becomes difficult. When the upper limit of conditional expression (4) is exceeded, it is difficult to correct chromatic aberration. Because Rs/f is equal to 1.077 in the present example, it is easy to cement the cemented lens and chromatic aberration is corrected satisfactorily.

[0089] When f is the focal point distance of the entire lens system, f41 is the focal point distance of the object side lens 17, and f42 is the focal point distance of the image side lens 18, the imaging lens 10 of the present example satisfies the following conditional expression (5).

3.0(f41/f42)/f1.5(5)

[0090] When (f41/f42)/f falls below the lower limit of conditional expression (5), it is difficult to achieve balance with axial chromatic aberration and magnification chromatic aberration, leading to loss of resolution in the peripheral portions of the image. When the upper limit of conditional expression (5) is exceeded, it is difficult to correct chromatic aberration. Because (f41/f42)/f is equal to 1.54 in the present example, the decrease in resolution can be suppressed, and chromatic aberration is corrected satisfactorily.

[0091] In the imaging lens 10 of the present example, when R31 is the radius of curvature of the object side lens surface 13a of the third lens 13 and R32 is the radius of curvature of the image side lens surface 13b of the third lens 13, R31 is equal to 3.573, R32 is equal to 5.766, and the following conditional expression (6) is satisfied.

R31|R32|(6)

[0092] In the imaging lens 10 of the present example, the Abbe number of the first lens 11, the second lens 12, and the image side lens 18 is 40 or greater, and the Abbe number of the third lens 13 and the object side lens 17 is 31 or less, whereby chromatic aberration is corrected.

[0093] When the F number of the imaging lens 10 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0094] Fno=2.0

[0095] =99.4

[0096] L=16.089 mm

[0097] When f represents the focal point distance of the entire lens system, f1 represents the focal point distance of the first lens 11, f2 represents the focal point distance of the second lens 12, f3 represents the focal point distance of the third lens 13, f4 represents the focal point distance of the fourth lens 14, f41 represents the focal point distance of the object side lens 17, and f42 represents the focal point distance of the image side lens 18, these values are as follows.

[0098] f=1.155 mm

[0099] f1=8.193 mm

[0100] f2=2.685 mm

[0101] f3=4.126 mm

[0102] f4=3.275 mm

[0103] f41=3.351 mm

[0104] f42=1.885 mm

[0105] Next, table 1A shows lens data of the lens surfaces of the imaging lens 10. In table 1A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 15, and surfaces 12 and 13 are the object side glass surface and the image side glass surface of the plate glass 16. Radius of curvature and gap are in units of millimeters. The values of Nd (refractive index) and d (Abbe number) of surface 10 represent values of the resin adhesive layer B1.

TABLE-US-00001 TABLE 1A Nd Vd Radius of (ref. (Abbe Surface Curvature Gap index) no.) 1 17.158 1.000 1.77250 49.6 2 4.506 2.903 3* 56.607 1.415 1.53461 56.0 4* 1.485 1.595 5* 3.573 2.087 1.58246 30.1 6* 5.766 0.866 7 infinity 0.923 8* 3.465 0.500 1.63494 24.0 9* 1.244 0.020 1.50000 50.0 10* 1.251 2.107 1.53461 56.0 11* 2.145 1.000 12 infinity 0.600 1.51680 64.2 13 infinity 1.074

[0106] Next, table 1B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 1B as well.

TABLE-US-00002 TABLE 1B 3rd surface 4th surface 5th surface 6th surface 8th surface K 2.84625E+01 1.40499E+00 5.08590E+00 0.00000E+00 1.31742E+00 A4 7.73159E04 9.48358E03 1.29842E02 1.24404E02 1.27224E02 A6 8.83607E06 8.23544E04 7.37044E04 2.28103E03 1.37903E03 A8 8.27198E07 2.00365E04 8.09568E05 9.57643E04 0.00000E+00 A10 2.49701E08 3.23758E05 1.68861E06 9.26933E05 0.00000E+00 A12 0.00000E+00 0.00000E+00 2.05962E06 0.00000E+00 0.00000E+00 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 9th surface 10th surface 11th surface K 5.22053E01 5.18954E01 5.07127E01 A4 2.05512E03 1.55213E02 2.38843E02 A6 2.12211E02 2.25983E02 2.51814E03 A8 5.63452E03 8.00738E03 1.41188E03 A10 4.54812E03 4.55649E03 2.09677E04 A12 9.87494E04 7.63457E04 3.07858E05 A14 0.00000E+00 0.00000E+00 1.16261E05 A16 0.00000E+00 0.00000E+00 0.00000E+00

[0107] The aspheric shape employed for the lens surfaces is expressed by the following formula, wherein Y is the amount of sag, c is the inverse of the radius of curvature, K is the conical coefficient, h is the height of the light ray, and A4, A6, A8, A10, A12, A14, and A16 are aspheric coefficients of the fourth degree, the sixth degree, the eighth degree, the tenth degree, the twelfth degree, the fourteenth degree, and the sixteenth degree, respectively.

[00001]$\begin{array}{cc}Y\left(h\right)=\frac{c.Math.h^2}{1+\sqrt{1-\left(K+1\right).Math.c^2.Math.h^2}}+A_4.Math.h^4+A_6.Math.h^6+A_8.Math.h^8+A_{10}.Math.h^{10}+A_{1.Math.2}.Math.h^{12}+A_{1.Math.4}.Math.h^{1.Math.4}+A_{16}.Math.h^{1.Math.6}& \left[\mathrm{Formula}.Math..Math.1\right]\end{array}$

[0108] (Effects)

[0109] FIGS. 3A to 3D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 10. In the longitudinal aberration graph of FIG. 3A, the horizontal axis represents the position where the light ray crosses the optical axis L1, and the vertical axis represents the height at the pupil radius. In the lateral aberration graphs of FIG. 3B, the horizontal axes represent entrance pupil coordinates, and the vertical axes represent the amount of aberration. In FIGS. 3A and 3B, simulation results are shown for a plurality of light rays of different wavelengths. In the field curvature graph of FIG. 3C, the horizontal axis represents distance in the direction of the optical axis L1, and the vertical axis represents the height of the image. In FIG. 3C, S represents field curvature aberration in the sagittal plane, and T represents field curvature aberration in the tangential plane. In the distortion aberration graph of FIG. 3D, the horizontal axis represents the amount of image distortion, and the vertical axis represents the height of the image.

[0110] According to the imaging lens 10 of the present example, axial chromatic aberration is satisfactorily corrected as shown in FIG. 3A. Color bleeding is also suppressed as shown in FIG. 3B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 3A and 3B. Furthermore, according to the imaging lens 10 of the present example, field curvature is satisfactorily corrected as shown in FIG. 3C. Therefore, the imaging lens 10 has high resolution.

[0111] In the present example, the imaging lens 10 is designed with a gap of 20 m or greater set in advance on the optical axis L1, between the image side lens surface 17b of the object side lens 17 and the object side lens surface 18a of the image side lens 18. Therefore, when the lens is being designed, it is possible to account for plus-side shifting of the field curvature in the tangential plane, which occurs due to the resin adhesive layer B1 thickening. Therefore, according to the imaging lens 10 of the present example, plus-side shifting of the field curvature in the tangential plane is suppressed as shown in FIG. 3C.

[0112] Next, FIG. 4 is a spherical aberration graph of the imaging lens 10, wherein the solid line represents spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray). The dashed line represents spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray). The horizontal axis of the spherical aberration graph represents the position where the light ray crosses the optical axis, and the vertical axis represents the height of the pupil radius. In the imaging lens 10, spherical aberration relative to a light ray with a wavelength of 850 nm is corrected as shown in FIG. 4, and there is no need for adjusting the focus between photographing under a visible light ray and photographing under a near infrared ray. In other words, in the imaging lens 10 of the present example, the occurrence of focus misalignment is suppressed between photographing using a visible light ray and photographing using a near infrared ray. In cases in which the fourth lens 14 is configured from a single lens that is not a cemented lens, it is difficult to correct both spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray) and spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray) in a balanced manner, and also to ensure that focus misalignment does not occur between photographing using a visible light ray and photographing using a near infrared ray.

Example 2

[0113] FIG. 5 is a configuration diagram (light ray diagram) of an imaging lens of Example 2. An imaging lens 20 of the present example comprises, in order from an object side to an image side, a first lens 21 having negative power, a second lens 22 having negative power, a third lens 23 having positive power, and a fourth lens 24 having positive power, as shown in FIG. 5. A diaphragm 25 is disposed between the third lens 23 and the fourth lens 24, and plate glass 26 is disposed on the image side of the fourth lens 24. An image-forming surface 12 is in a separate position from the plate glass 26. The fourth lens 24 is a cemented lens comprising an object side lens 27 having negative power and an image side lens 28 having positive power. The object side lens 27 and the image side lens 28 are bonded by a resin adhesive, and a resin adhesive layer B2 is formed between the object side lens 27 and the image side lens 28. The shapes of the lenses constituting the imaging lens 20 of the present example are the same as the shapes of the lenses corresponding to the imaging lens 10 of Example 1, and descriptions thereof are therefore omitted.

[0114] When the F number of the imaging lens 20 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0115] Fno=2.0

[0116] =97.6

[0117] L=15.598 mm

[0118] When f is the focal point distance of the entire lens system, f1 is the focal point distance of the first lens 21, f2 is the focal point distance of the second lens 22, f3 is the focal point distance of the third lens 23, f4 is the focal point distance of the fourth lens 24, f41 is the focal point distance of the object side lens 27, and f42 is the focal point distance of the image side lens 28, these values are as follows.

[0119] f=1.141 mm

[0120] f1=8.378 mm

[0121] f2=2.600 mm

[0122] f3=4.060 mm

[0123] f4=3.199 mm

[0124] f41=3.520 mm

[0125] f42=1.829 mm

[0126] In the imaging lens 20 of the present example, when D is the thickness of the resin adhesive layer B2 on the optical axis L2, Sg1H is the amount of sag in the image side lens surface 27b of the object side lens 27 at height H in the effective diameter of the image side lens surface 27b of the object side lens 27 in a direction orthogonal to the optical axis L2, Sg2H is the amount of sag in the object side lens surface 28a of the image side lens 28 at height H, Rs is the radius of curvature of the image side lens surface 27b of the object side lens 27, R31 is the radius of curvature of the object side lens surface 23a of the third lens 23, and R32 is the radius of curvature of the image side lens surface 23b of the third lens 23, then the conditional expressions (1) to (6) given in the description of Example 1 are satisfied, and the values of the conditional expressions (1) and (3) to (6) are as follows.

20 mD=20 m(1)

Sg1HSg2H(2)

D=20 m100 m(3)

0.9Rs/f=1.1121.3(4)

3.0(f41/f42)/f=1.691.5(5)

R31=3.428|R32|=|5.958|(6)

[0127] Furthermore, in the imaging lens 20 of the present example, the Abbe number of the first lens 21, the second lens 22, and the image side lens 28 is 40 or greater, and the Abbe number of the third lens 23 and the object side lens 27 is 31 or less, whereby chromatic aberration is corrected.

[0128] Next, table 2A shows lens data of the lens surfaces of the imaging lens 20. In table 2A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 25, and surfaces 12 and 13 are the object side glass surface and the image side glass surface of the plate glass 26. Radius of curvature and gap are in units of millimeters. The values of Nd (refractive index) and d (Abbe number) of the tenth surface represent values of the resin adhesive layer B2.

TABLE-US-00003 TABLE 2A Nd Vd Radius of (ref. (Abbe Surface Curvature Gap index) no.) 1 16.082 1.000 1.77250 49.6 2 4.490 2.831 3* 52.186 1.348 1.53461 56.0 4* 1.441 1.594 5* 3.428 2.037 1.58246 30.1 6* 5.958 0.829 7 infinity 0.909 8* 3.388 0.500 1.63494 24.0 9* 1.269 0.020 1.50000 50.0 10* 1.270 1.785 1.53461 56.0 11* 2.169 1.000 12 infinity 0.800 1.51680 64.2 13 infinity 0.946

[0129] Next, table 2B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 2B as well.

TABLE-US-00004 TABLE 2B 3rd surface 4th surface 5th surface 6th surface 8th surface K 4.85524E+01 1.34758E+00 5.03141E+00 0.00000E+00 1.36928E+00 A4 6.08537E04 1.01062E02 1.36480E02 1.41031E02 1.15999E02 A6 1.09398E05 6.68407E04 6.11024E04 2.61724E03 1.63819E03 A8 3.28794E07 1.40973E04 1.03327E04 8.52922E04 0.00000E+00 A10 1.20383E08 3.09290E05 1.60209E05 7.04918E05 0.00000E+00 A12 0.00000E+00 0.00000E+00 1.74143E06 0.00000E+00 0.00000E+00 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 9th surface 10th surface 11th surface K 4.83880E01 4.77306E01 5.52365E01 A4 5.41293E03 9.13101E02 2.11256E02 A6 1.93570E02 1.66609E02 1.21540E03 A8 4.66595E03 8.41125E03 1.48351E03 A10 4.64886E03 5.56732E03 2.54428E04 A12 9.51682E04 8.11428E04 2.89948E05 A14 0.00000E+00 0.00000E+00 1.92218E05 A16 0.00000E+00 0.00000E+00 0.00000E+00

[0130] (Effects)

[0131] FIGS. 6A to 6D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 20. According to the imaging lens 20, axial chromatic aberration is satisfactorily corrected as shown in FIG. 6A. Color bleeding is also suppressed as shown in FIG. 6B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 6A and 6B. Furthermore, according to the imaging lens 20 of the present example, field curvature is satisfactorily corrected as shown in FIG. 6C. Therefore, the imaging lens 20 has high resolution.

[0132] In the present example, the imaging lens 20 is designed with a gap of 20 m or greater set in advance on the optical axis L2, between the image side lens surface 27b of the object side lens 27 and the object side lens surface 28a of the image side lens 28. Therefore, when the lens is being designed, it is possible to account for plus-side shifting of the field curvature in the tangential plane, which occurs due to the resin adhesive layer B2 thickening. Therefore, according to the imaging lens 20 of the present example, plus-side shifting of the field curvature in the tangential plane is suppressed as shown in FIG. 6C.

[0133] Next, FIG. 7 is a spherical aberration graph of the imaging lens 20, wherein the solid line represents spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray). The dashed line represents spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray). The horizontal axis of the spherical aberration graph represents the position where the light ray crosses the optical axis, and the vertical axis represents the height of the pupil radius. In the imaging lens 20, spherical aberration relative to a light ray with a wavelength of 850 nm is corrected as shown in FIG. 7, and there is no need for adjusting the focus between photographing under a visible light ray and photographing under a near infrared ray. In other words, in the imaging lens 20 of the present example, the occurrence of focus misalignment is suppressed between photographing using a visible light ray and photographing using a near infrared ray.

Example 3

[0134] FIG. 8 is a configuration diagram (light ray diagram) of an imaging lens of Example 3. An imaging lens 30 of the present example comprises, in order from an object side to an image side, a first lens 31 having negative power, a second lens 32 having negative power, a third lens 33 having positive power, and a fourth lens 34 having positive power, as shown in FIG. 8. A diaphragm 35 is disposed between the third lens 33 and the fourth lens 34, and plate glass 36 is disposed on the image side of the fourth lens 34. An image-forming surface 13 is in a separate position from the plate glass 36. The fourth lens 34 is a cemented lens comprising an object side lens 37 having negative power and an image side lens 38 having positive power. The object side lens 37 and the image side lens 38 are bonded by a resin adhesive, and a resin adhesive layer B3 is formed between the object side lens 37 and the image side lens 38. The shapes of the lenses constituting the imaging lens 30 of the present example are the same as the shapes of the lenses corresponding to the imaging lens 10 of Example 1, and descriptions thereof are therefore omitted.

[0135] When the F number of the imaging lens 30 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0136] Fno=2.0

[0137] =96.0

[0138] L=12.637 mm

[0139] When f represents the focal point distance of the entire lens system, f1 represents the focal point distance of the first lens 31, f2 represents the focal point distance of the second lens 32, f3 represents the focal point distance of the third lens 33, f4 represents the focal point distance of the fourth lens 34, f41 represents the focal point distance of the object side lens 37, and f42 represents the focal point distance of the image side lens 38 these values are as follows.

[0140] f=0.847 mm

[0141] f1=5.553 mm

[0142] f2=1.712 mm

[0143] f3=2.742 mm

[0144] f4=2.317 mm

[0145] f41=2.670 mm

[0146] f42=1.493 mm

[0147] In the imaging lens 30 of the present example, when D represents the thickness of the resin adhesive layer B3 on the optical axis L3, Sg1H represents the amount of sag in the image side lens surface 37b of the object side lens 37 at height H in the effective diameter of the image side lens surface 37b of the object side lens 37 in a direction orthogonal to the optical axis L3, Sg2H represents the amount of sag in the object side lens surface 38a of the image side lens 38 at height H, Rs represents the radius of curvature of the image side lens surface 37b of the object side lens 37, R31 represents the radius of curvature of the object side lens surface 33a of the third lens 33, and R32 represents the radius of curvature of the image side lens surface 33b of the third lens 33, then the conditional expressions (1) to (6) given in the description of Example 1 are satisfied, and the values of the conditional expressions (1) and (3) to (6) are as follows.

20 mD=20 m(1)

Sg1HSg2H(2)

D=20 m100 m(3)

0.9Rs/f=1.1031.3(4)

3.0(f41/f42)/f=2.111.5(5)

R31=1.824|R32|=|8.292|(6)

[0148] Furthermore, in the imaging lens 30 of the present example, the Abbe number of the first lens 31, the second lens 32, and the image side lens 38 is 40 or greater, and the Abbe number of the third lens 33 and the object side lens 37 is 31 or less, whereby chromatic aberration is corrected.

[0149] Next, table 3A shows lens data of the lens surfaces of the imaging lens 30. In table 3A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 35, and surfaces 12 and 13 are the object side glass surface and the image side glass surface of the plate glass 36. Radius of curvature and gap are in units of millimeters. The values of Nd (refractive index) and d (Abbe number) of the tenth surface represent values of the resin adhesive layer B3.

TABLE-US-00005 TABLE 3A Nd Vd Radius of (ref. (Abbe Surface Curvature Gap index) no.) 1 15.167 1.000 1.77250 49.6 2 3.248 2.137 3* 82.115 1.192 1.53461 56.0 4* 0.930 0.833 5* 1.824 1.754 1.58246 30.1 6* 8.292 1.047 7 infinity 0.267 8* 2.522 0.500 1.63232 23.3 9* 0.934 0.020 1.50000 50.0 10* 0.985 1.881 1.53461 56.0 11* 1.407 1.000 12 infinity 0.300 1.51680 64.2 13 infinity 0.707

[0150] Next, table 3B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 3B as well.

TABLE-US-00006 TABLE 3B 3rd surface 4th surface 5th surface 6th surface 8th surface K 3.60256E+0 1.06928E+OO.sup. 1.33964E+00 0.00000E+00 2.70264E+00 A4 1.66270E03 2.14019E02 3.98212E02 4.99316E02 6.76570E02 A6 2.50310E05 1.35178E02 1.87024E03 2.94229E02 0.00000E+00 A8 4.90298E06 3.07720E03 1.72035E03 1.41316E02 0.00000E+00 A10 3.49239E07 4.65455E04 8.49190E04 2.20487E03 0.00000E+00 A12 0.00000E+00 0.00000E+00 6.45946E05 0.00000E+00 0.00000E+00 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 9th surface 10th surface 11th surface K 4.48387E01 8.31760E01 5.28763E01 A4 6.46831E02 1.97069E01 6.63000E02 A6 6.49574E02 2.33004E01 3.07803E02 A8 1.82272E01 5.31866E02 2.74275E02 A10 2.14111E01 8.43919E02 8.24114E03 A12 7.23247E02 0.00000E+00 1.10075E03 A14 0.00000E+00 0.00000E+00 2.46844E04 A16 0.00000E+00 0.00000E+00 0.00000E+00

[0151] (Effects)

[0152] FIGS. 9A to 9D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 30. According to the imaging lens 30, axial chromatic aberration is satisfactorily corrected as shown in FIG. 9A. Color bleeding is also suppressed as shown in FIG. 9B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 9A and 9B. Furthermore, according to the imaging lens 30 of the present example, field curvature is satisfactorily corrected as shown in FIG. 9C. Therefore, the imaging lens 30 has high resolution.

[0153] In the present example, the imaging lens 30 is designed with a gap of 20 m or greater set in advance on the optical axis L3, between the image side lens surface 37b of the object side lens 37 and the object side lens surface 38a of the image side lens 38. Therefore, when the lens is being designed, it is possible to account for plus-side shifting of the field curvature in the tangential plane, which occurs due to the resin adhesive layer B3 thickening. Therefore, according to the imaging lens 30 of the present example, plus-side shifting of the field curvature in the tangential plane is suppressed as shown in FIG. 9C.

[0154] Next, FIG. 10 is a spherical aberration graph of the imaging lens 30, wherein the solid line represents spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray). The dashed line represents spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray). The horizontal axis of the spherical aberration graph represents the position where the light ray crosses the optical axis, and the vertical axis represents the height of the pupil radius. In the imaging lens 30, spherical aberration relative to a light ray with a wavelength of 850 nm is corrected as shown in FIG. 10, and there is no need for adjusting the focus between photographing under a visible light ray and photographing under a near infrared ray. In other words, in the imaging lens 30 of the present example, the occurrence of focus misalignment is suppressed between photographing using a visible light ray and photographing using a near infrared ray.

Example 4

[0155] FIG. 11 is a configuration diagram (light ray diagram) of an imaging lens of Example 4. An imaging lens 40 of the present example comprises, in order from an object side to an image side, a first lens 41 having negative power, a second lens 42 having negative power, a third lens 43 having positive power, and a fourth lens 44 having positive power, as shown in FIG. 8. A diaphragm 45 is disposed between the third lens 43 and the fourth lens 44, and plate glass 46 is disposed on the image side of the fourth lens 44. An image-forming surface 14 is in a separate position from the plate glass 46. The fourth lens 44 is a cemented lens comprising an object side lens 47 having negative power and an image side lens 48 having positive power. The object side lens 47 and the image side lens 48 are bonded by a resin adhesive, and a resin adhesive layer B4 is formed between the object side lens 47 and the image side lens 48. The shapes of the lenses constituting the imaging lens 40 of the present example are the same as the shapes of the lenses corresponding to the imaging lens 10 of Example 1, and descriptions thereof are therefore omitted.

[0156] When the F number of the imaging lens 40 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0157] Fno=2.0

[0158] =96.0

[0159] L=13.514 mm

[0160] When f represents the focal point distance of the entire lens system, f1 represents the focal point distance of the first lens 41, f2 represents the focal point distance of the second lens 42, f3 represents the focal point distance of the third lens 43, f4 represents the focal point distance of the fourth lens 44, f41 represents the focal point distance of the object side lens 47, and f42 represents the focal point distance of the image side lens 48, these values are as follows.

[0161] f=0.994 mm

[0162] f1=8.279 mm

[0163] f2=1.785 mm

[0164] f3=2.929 mm

[0165] f4=2.394 mm

[0166] f41=3.114 mm

[0167] f42=1.479 mm

[0168] In the imaging lens 40 of the present example, when D represents the thickness of the resin adhesive layer B4 on the optical axis L4, Sg1H represents the amount of sag in the image side lens surface 47b of the object side lens 47 at height H in the effective diameter of the image side lens surface 47b of the object side lens 47 in a direction orthogonal to the optical axis L4, Sg2H represents the amount of sag in the object side lens surface 48a of the image side lens 48 at height H, Rs represents the radius of curvature of the image side lens surface 47b of the object side lens 47, R31 represents the radius of curvature of the object side lens surface 43a of the third lens 43, and R32 represents the radius of curvature of the image side lens surface 43b of the third lens 43, then the conditional expressions (1) to (6) given in the description of Example 1 are satisfied, and the values of the conditional expressions (1) and (3) to (6) are as follows.

20 mD=20 m(1)

Sg1HSg2H(2)

D=20 m100 m(3)

0.9Rs/f=1.1891.3(4)

3.0(f41/f42)/f=2.121.5(5)

R31=2.115|R32|=|5.863|(6)

[0169] Furthermore, in the imaging lens 40 of the present example, the Abbe number of the first lens 41, the second lens 42, and the image side lens 48 is 40 or greater, and the Abbe number of the third lens 43 and the object side lens 47 is 31 or less, whereby chromatic aberration is corrected.

[0170] Next, table 4A shows lens data of the lens surfaces of the imaging lens 40. In table 4A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 45, and surfaces 12 and 13 are the object side glass surface and the image side glass surface of the plate glass 46. Radius of curvature and gap are in units of millimeters. The values of Nd (refractive index) and d (Abbe number) of the tenth surface represent values of the resin adhesive layer B4.

TABLE-US-00007 TABLE 4A Radius of Nd (ref. Vd (Abbe Surface Curvature Gap index) no.) 1 19.042 1.000 1.58913 61.3 2 3.807 2.812 3* 11.513 1.548 1.54410 56.1 4* 1.111 0.472 5* 2.115 1.930 1.58250 30.2 6* 5.863 0.929 7 infinity 0.371 8* 3.389 0.500 1.63980 23.3 9* 1.182 0.020 1.51313 53.9 10* 1.135 1.489 1.54410 56.1 11* 1.487 1.000 12 infinity 0.300 1.51680 64.2 13 infinity 1.143

[0171] Next, table 4B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 4B as well.

TABLE-US-00008 TABLE 4B 3rd surface 4th surface 5th surface 6th surface 8th surface K 0.00000E+00 1.14072E+00 1.65827E+00 6.16240E+00 3.81816E+00 A4 1.60230E03 1.77641E02 3.73407E02 4.78862E02 4.94012E02 A6 6.88899E06 1.55775E02 3.26048E03 1.99747E02 1.07795E01 A8 8.41573E06 2.55153E03 1.80394E03 1.50700E03 3.28112E01 A10 6.48226E08 2.92172E05 9.45624E04 1.79524E02 4.00692E01 A12 1.39532E08 5.56951E06 4.05919E05 1.36560E02 9.62778E02 A14 0.00000E+00 0.00000E+00 0.00000E+00 4.66022E03 1.32539E01 A16 0.00000E+00 0.00000E+00 0.00000E+00 6.74695E04 6.80049E02 9th surface 10th surface 11th surface K 3.72777E01 4.73549E01 4.35515E01 A4 1.04207E02 6.80388E02 4.43706E02 A6 1.42219E01 6.47585E02 1.90538E02 A8 1.30746E03 1.30859E02 2.58744E02 A10 3.22870E02 1.30450E02 8.505886E03 A12 1.66066E02 1.64851E02 1.57286E03 A14 3.12449E03 1.03073E02 7.60301E05 A16 9.02035E03 1.04512E02 1.29595E04

[0172] (Effects)

[0173] FIGS. 12A to 12D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 40. According to the imaging lens 40, axial chromatic aberration is satisfactorily corrected as shown in FIG. 12A. Color bleeding is also suppressed as shown in FIG. 12B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 12A and 12B. Furthermore, according to the imaging lens 40 of the present example, field curvature is satisfactorily corrected as shown in FIG. 12C. Therefore, the imaging lens 40 has high resolution.

[0174] In the present example, the imaging lens 40 is designed with a gap of 20 m or greater set in advance on the optical axis L4, between the image side lens surface 47b of the object side lens 47 and the object side lens surface 48a of the image side lens 48. Therefore, when the lens is being designed, it is possible to account for plus-side shifting of the field curvature in the tangential plane, which occurs due to the resin adhesive layer B4 thickening. Therefore, according to the imaging lens 40 of the present example, plus-side shifting of the field curvature in the tangential plane is suppressed as shown in FIG. 12C.

[0175] Next, FIG. 13 is a spherical aberration graph of the imaging lens 40, wherein the solid line represents spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray). The dashed line represents spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray). The horizontal axis of the spherical aberration graph represents the position where the light ray crosses the optical axis, and the vertical axis represents the height of the pupil radius. In the imaging lens 40, spherical aberration relative to a light ray with a wavelength of 850 nm is corrected as shown in FIG. 13, and there is no need for adjusting the focus between photographing under a visible light ray and photographing under a near infrared ray. In other words, in the imaging lens 40 of the present example, the occurrence of focus misalignment is suppressed between photographing using a visible light ray and photographing using a near infrared ray.

Example 5

[0176] FIG. 14 is a configuration diagram (light ray diagram) of an imaging lens of Example 5. An imaging lens 50 of the present example comprises, in order from an object side to an image side, a first lens 51 having negative power, a second lens 52 having negative power, a third lens 53 having positive power, and a fourth lens 54 having positive power, as shown in FIG. 14. A diaphragm 55 is disposed between the third lens 53 and the fourth lens 54, and plate glass 56 is disposed on the image side of the fourth lens 54. An image-forming surface 15 is in a separate position from the plate glass 56. The fourth lens 54 is a cemented lens comprising an object side lens 57 having negative power and an image side lens 58 having positive power. The object side lens 57 and the image side lens 58 are bonded by a resin adhesive, and a resin adhesive layer B5 is formed between the object side lens 57 and the image side lens 58. The shapes of the lenses constituting the imaging lens 50 of the present example are the same as the shapes of the lenses corresponding to the imaging lens 10 of Example 1, and descriptions thereof are therefore omitted.

[0177] When the F number of the imaging lens 50 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0178] Fno=2.0

[0179] =100.0

[0180] L=19.664 mm

[0181] When f is the focal point distance of the entire lens system, f1 is the focal point distance of the first lens 51, f2 is the focal point distance of the second lens 52, f3 is the focal point distance of the third lens 53, f4 is the focal point distance of the fourth lens 54, f41 is the focal point distance of the object side lens 57, and f42 is the focal point distance of the image side lens 58, these values are as follows.

[0182] f=1.248 mm

[0183] f1=8.890 mm

[0184] f2=2.602 mm

[0185] f3=4.265 mm

[0186] f4=3.481 mm

[0187] f41=4.227 mm

[0188] f42=1.479 mm

[0189] In the imaging lens 50 of the present example, when D is the thickness of the resin adhesive layer B5 on the optical axis L5, Sg1H is the amount of sag in the image side lens surface 57b of the object side lens 57 at height H in the effective diameter of the image side lens surface 57b of the object side lens 57 in a direction orthogonal to the optical axis L5, Sg2H is the amount of sag in the object side lens surface 58a of the image side lens 58 at height H, Rs is the radius of curvature of the image side lens surface 57b of the object side lens 57, R31 is the radius of curvature of the object side lens surface 53a of the third lens 53, and R32 is the radius of curvature of the image side lens surface 53b of the third lens 53, then the conditional expressions (1) to (6) given in the description of Example 1 are satisfied, and the values of the conditional expressions (1) and (3) to (6) are as follows.

20 mD=20 m(1)

Sg1HSg2H(2)

D=20 m100 m(3)

0.9Rs/f=1.1201.3(4)

3.0(f41/f42)/f=1.501.5(5)

R31=2.828|R32|=|13.176|(6)

[0190] Furthermore, in the imaging lens 50 of the present example, the Abbe number of the first lens 51, the second lens 52, and the image side lens 58 is 40 or greater, and the Abbe number of the third lens 53 and the object side lens 57 is 31 or less, whereby chromatic aberration is corrected.

[0191] Next, table 5A shows lens data of the lens surfaces of the imaging lens 50. In table 5A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 55, and surfaces 12 and 13 are the object side glass surface and the image side glass surface of the plate glass 56. Radius of curvature and gap are in units of millimeters. The values of Nd (refractive index) and d (Abbe number) of the tenth surface represent values of the resin adhesive layer B5.

TABLE-US-00009 TABLE 5A Nd Vd Radius of (ref. (Abbe Surface Curvature Gap index) no.) 1 23.391 1.494 1.7725 49.6 2 5.161 3.317 3* 89.639 1.888 1.5346 56.27 4* 1.423 1.373 5* 2.828 2.729 1.5825 30.18 6* 13.176 1.471 7 infinity 0.651 8* 3.582 0.820 1.63493 23.89 9* 1.398 0.020 1.5 50 10* 1.409 3.038 1.5346 56.27 11* 2.097 1.000 12 infinity 0.600 1.5168 64.2 13 infinity 1.263

[0192] Next, table 5B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 5B as well.

TABLE-US-00010 TABLE 5B 3rd surface 4th surface 5th surface 6th surface 8th surface K 6.03211E+01 1.09619E+00 1.54839E+00 0.00000E+00 1.98881E+00 A4 6.38352E04 5.25824E03 1.12674E02 1.36867E02 1.69038E02 A6 3.34872E06 1.58711E03 2.76736E04 3.62175E03 0.00000E+00 A8 2.84477E07 1.49809E04 7.57961E05 8.49297E04 0.00000E+00 A10 8.74143E09 8.75115E06 1.91559E05 6.65457E05 0.00000E+00 A12 0.00000E+00 0.00000E+00 8.62848E07 0.00000E+00 0.00000E+00 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 9th surface 10th surface 11th surface K 3.94577E01 1.02230E+00 5.74699E01 A4 3.53157E03 5.32513E02 1.90393E02 A6 1.92894E02 2.50742E02 3.09208E03 A8 6.20294E03 2.79467E03 1.24752E03 A10 4.93769E03 2.06775E03 1.89301E04 A12 9.98388E04 0.00000E+00 1.45505E05 A14 0.00000E+00 0.00000E+00 8.37640E07 A16 0.00000E+00 0.00000E+00 0.00000E+00

[0193] (Effects)

[0194] FIGS. 15A to 15D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 50. According to the imaging lens 50, axial chromatic aberration is satisfactorily corrected as shown in FIG. 15A. Color bleeding is also suppressed as shown in FIG. 15B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 15A and 15B. Furthermore, according to the imaging lens 50 of the present example, field curvature is satisfactorily corrected as shown in FIG. 15C. Therefore, the imaging lens 50 has high resolution.

[0195] In the present example, the imaging lens 50 is designed with a gap of 20 m or greater set in advance on the optical axis L5, between the image side lens surface 57b of the object side lens 57 and the object side lens surface 58a of the image side lens 58. Therefore, when the lens is being designed, it is possible to account for plus-side shifting of the field curvature in the tangential plane, which occurs due to the resin adhesive layer B5 thickening. Therefore, according to the imaging lens 50 of the present example, plus-side shifting of the field curvature in the tangential plane is suppressed as shown in FIG. 15C.

[0196] Next, FIG. 16 is a spherical aberration graph of the imaging lens 50, wherein the solid line represents spherical aberration relative to a light ray with a wavelength of 588 nm (a visible light ray). The dashed line represents spherical aberration relative to a light ray with a wavelength of 850 nm (a near infrared ray). The horizontal axis of the spherical aberration graph represents the position where the light ray crosses the optical axis, and the vertical axis represents the height of the pupil radius. In the imaging lens 50, spherical aberration relative to a light ray with a wavelength of 850 nm is corrected as shown in FIG. 16, and there is no need for adjusting the focus between photographing under a visible light ray and photographing under a near infrared ray. In other words, in the imaging lens 50 of the present example, the occurrence of focus misalignment is suppressed between photographing using a visible light ray and photographing using a near infrared ray.

Other Embodiments

[0197] In the image-capturing lenses 10 to 50 described above, the image side lens surfaces (13b, 23b, 33b, 43b, 53b) of the third lenses have convex curved portions that have negative curvature and protrude progressively farther toward the image side along the optical axis, but these image side lens surfaces (13b, 23b, 33b, 43b, 53b) may have concave curved portions that have positive curvature and cave progressively farther toward the object side along the optical axis. It is easy in this case as well to make the image-capturing lenses 10 to 50 into wide angle lenses by satisfying conditional expression (6).

[0198] (Imaging Device)

[0199] FIG. 17 is an explanatory diagram of an imaging device equipped with an imaging lens of the present invention. The imaging device 60 has an image pick-up device 61 in which a sensor surface 61a is disposed on the image-forming surface I1 (focal point position) of the imaging lens 10, as shown in FIG. 17. The image pick-up device 61 is a CCD sensor or a CMOS sensor.

[0200] According to the present example, because the imaging lens has high resolution, the imaging device 60 can be made to have high resolution by employing an image pick-up device with a high number of pixels as the image pick-up device 61. The imaging device 60 herein can be equipped with any of the imaging lenses 20 to 50 in the same manner as the imaging lens 10, in which case the same effects can be achieved.

[0201] The imaging device 60 can be made into an imaging device that utilizes a near infrared ray and a visible light ray by disposing an optical filter 62, which transmits a visible light ray and a near infrared ray of a range including a wavelength of 850 nm and guides the light rays to the imaging lens 10, between the imaging lens 10 and the image pick-up device 61, as shown by the double-dotted line in FIG. 17. Specifically, the imaging lens 10 prevents or suppresses the occurrence of focus misalignment between photographing using a visible light ray and photographing using a near infrared ray. Therefore, merely equipping the imaging device 60 with the optical filter 62 makes it possible to configure an imaging device that performs both imaging utilizing a near infrared ray including a wavelength of 850 nm, i.e. a light ray in a range of 800 nm to 1100 nm for example, and imaging utilizing a visible light ray, i.e. visible light with a wavelength of 400 nm to 700 nm. The occurrence of focus misalignment between photographing using a visible light ray and photographing using a near infrared ray is prevented or suppressed in the imaging lenses 20 to 50 as well. Therefore, merely equipping the imaging device 60 with the optical filter 62 makes it possible to configure an imaging device that performs both imaging utilizing a near infrared ray including a wavelength of 850 nm and imaging utilizing a visible light ray, similar to cases of using the imaging lens 10. The optical filter 62 may be disposed on the object sides of the imaging lenses 10 to 50.

Reference Example 1

[0202] Imaging lenses of Reference Examples 1 to 3 are described below with reference to FIGS. 18 to 23. The imaging lenses of Reference Examples 1 to 3 have configurations similar to Examples 1 to 5, but the thickness along the optical axis of the resin adhesive layer bonding the two lenses constituting the cemented lens, i.e., the gap along the optical axis between the two lenses constituting the cemented lens, is less than 20 m.

[0203] FIG. 18 is a configuration diagram (light ray diagram) of an imaging lens of Reference Example 1. An imaging lens 70 of the present example comprises, in order from an object side to an image side, a first lens 71 having negative power, a second lens 72 having negative power, a third lens 73 having positive power, and a fourth lens 74 having positive power, as shown in FIG. 18. A diaphragm 75 is disposed between the third lens 73 and the fourth lens 74, and plate glass 76 is disposed on the image side of the fourth lens 74. An image-forming surface 17 is in a separate position from the plate glass 76. The fourth lens 74 is a cemented lens comprising an object side lens 77 having negative power and an image side lens 78 having positive power. An image side lens surface 77b of the object side lens 77 and an object side lens surface 78a of the image side lens 78, which constitute cemented surfaces of the cemented lens, have the same shape. The object side lens 77 and the image side lens 78 are bonded by a resin adhesive, but there is essentially zero gap between the object side lens 77 and the image side lens 78.

[0204] When the F number of the imaging lens 70 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0205] Fno=2.0

[0206] =88.6

[0207] L=12.499 mm

[0208] When f is the focal point distance of the entire lens system, f1 is the focal point distance of the first lens 71, f2 is the focal point distance of the second lens 72, f3 is the focal point distance of the third lens 73, f4 is the focal point distance of the fourth lens 74, f41 is the focal point distance of the object side lens 77, and f42 is the focal point distance of the image side lens 78, these values are as follows.

[0209] f=1.444 mm

[0210] f1=6.918 mm

[0211] f2=2.422 mm

[0212] f3=3.349 mm

[0213] f4=3.215 mm

[0214] f41=3.243 mm

[0215] f42=1.752 mm

[0216] In the imaging lens 70 of the present example, when Sg1H is the amount of sag in the image side lens surface 77b of the object side lens 77 at height H in the effective diameter of the image side lens surface 77b of the object side lens 77 in a direction orthogonal to the optical axis L7, Sg2H is the amount of sag in the object side lens surface 78a of the image side lens 78 at height H, Rs is the radius of curvature of the image side lens surface 77b of the object side lens 77, R31 is the radius of curvature of the object side lens surface 73a of the third lens 73, and R32 is the radius of curvature of the image side lens surface 73b of the third lens 73, then the conditional expressions (2), (5), and (6) given in the description of Example 1 are satisfied. The values of the conditional expressions (5) and (6) are as follows.

Sg1HSg2H(2)

3.0(f41/f42)/f=1.281.5(5)

R31=2.400|R32|=|8.121|(6)

[0217] Furthermore, in the imaging lens 70 of the present example, the Abbe number of the first lens 71, the second lens 72, and the image side lens 78 is 40 or greater, and the Abbe number of the third lens 73 and the object side lens 77 is 31 or less, whereby chromatic aberration is corrected.

[0218] In the imaging lens 70, Rs/f is equal to 0.848, which falls below the lower limit of conditional expression (4).

[0219] Next, table 6A shows lens data of the lens surfaces of the imaging lens 70. In table 6A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 75, and surfaces 11 and 12 are the object side glass surface and the image side glass surface of the plate glass 76. Radius of curvature and gap are in units of millimeters.

TABLE-US-00011 TABLE 6A Radius of Nd (ref. Vd (Abbe Surface Curvature Gap index) no.) 1 22.729 1.000 1.77250 49.6 2 4.244 1.568 3* 39.094 0.982 1.53461 56.0 4* 1.242 1.159 5* 2.400 1.439 1.58246 30.1 6* 8.121 0.982 7 infinity 0.253 0.253 8* 3.497 0.500 1.63494 24.0 9* 1.224 1.613 1.53461 56.0 10* 2.158 1.000 11 infinity 0.700 1.51680 64.2 12 infinity 1.303

[0220] Next, table 6B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 6B as well.

TABLE-US-00012 TABLE 6B 3rd surface 4th surface 5th surface 6th surface 8th surface 9th surface 10th surface K 0.00000E+00 1.10386E+00 2.85133E+00 0.00000E+00 4.41585E+00 4.03391E01 4.40846E01 A4 7.22684E04 9.69822E03 1.85742E02 2.04844E02 1.30111E02 3.93057E02 1.42869E02 A6 1.99874E05 2.41562E03 4.74678E03 1.76868E04 9.10184E03 6.30264E02 2.13805E03 A8 3.95429E06 5.68796E04 4.47446E04 4.19487E04 0.00000E+00 6.71597E04 1.85498E03 A10 1.77245E07 2.05578E04 2.82868E05 1.24097E04 0.00000E+00 7.59331E03 1.10425E03 A12 0.00000E+00 0.00000E+00 9.43715E06 0.00000E+00 0.00000E+00 3.65218E03 1.28829E04 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 2.71356E04 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0221] FIGS. 19A to 19D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 70. According to the imaging lens 70 of the present example, axial chromatic aberration is satisfactorily corrected as shown in FIG. 19A. Color bleeding is also suppressed as shown in FIG. 19B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 19A and 19B. Furthermore, according to the imaging lens 70 of the present example, field curvature is satisfactorily corrected as shown in FIG. 19C.

Reference Example 2

[0222] FIG. 20 is a configuration diagram (light ray diagram) of an imaging lens of Reference Example 2. An imaging lens 80 of the present example comprises, in order from an object side to an image side, a first lens 81 having negative power, a second lens 82 having negative power, a third lens 83 having positive power, and a fourth lens 84 having positive power, as shown in FIG. 20. A diaphragm 85 is disposed between the third lens 83 and the fourth lens 84, and plate glass 86 is disposed on the image side of the fourth lens 84. An image-forming surface 18 is in a separate position from the plate glass 86. The fourth lens 84 is a cemented lens comprising an object side lens 87 having negative power and an image side lens 88 having positive power. An image side lens surface 87b of the object side lens 87 and an object side lens surface 88a of the image side lens 88, which constitute cemented surfaces of the cemented lens, have the same shape. The object side lens 87 and the image side lens 88 are bonded by a resin adhesive, but there is essentially zero gap between the object side lens 87 and the image side lens 88.

[0223] When the F number of the imaging lens 80 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0224] Fno=2.0

[0225] =100.8

[0226] L=13.301 mm

[0227] When f is the focal point distance of the entire lens system, f1 is the focal point distance of the first lens 81, f2 is the focal point distance of the second lens 82, f3 is the focal point distance of the third lens 83, f4 is the focal point distance of the fourth lens 84, f41 is the focal point distance of the object side lens 87, and f42 is the focal point distance of the image side lens 88, these values are as follows.

[0228] f=1.187 mm

[0229] f1=6.813 mm

[0230] f2=2.080 mm

[0231] f3=3.061 mm

[0232] f4=3.238 mm

[0233] f41=2.699 mm

[0234] f42=1.743 mm

[0235] In the imaging lens 80 of the present example, when Sg1H is the amount of sag in the image side lens surface 87b of the object side lens 87 at height H in the effective diameter of the image side lens surface 87b of the object side lens 87 in a direction orthogonal to the optical axis L8, Sg2H is the amount of sag in the object side lens surface 88a of the image side lens 88 at height H, Rs is the radius of curvature of the image side lens surface 87b of the object side lens 87, R31 is the radius of curvature of the object side lens surface 83a of the third lens 83, and R32 is the radius of curvature of the image side lens surface 83b of the third lens 83, then the conditional expressions (2), (4), and (6) given in the description of Example 1 are satisfied. The values of the conditional expressions (4) and (6) are as follows.

Sg1HSg2H(2)

0.9Rs/f=1.0161.3(4)

R31=2.437|R32|=|5.274|(6)

[0236] Furthermore, in the imaging lens 80 of the present example, the Abbe number of the first lens 81, the second lens 82, and the image side lens 88 is 40 or greater, and the Abbe number of the third lens 83 and the object side lens 87 is 31 or less, whereby chromatic aberration is corrected.

[0237] In the imaging lens 80, (f41/f42)/f is equal to 1.30, which exceeds the upper limit of conditional expression (5).

[0238] Next, table 7A shows lens data of the lens surfaces of the imaging lens 80. In table 7A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 85, and surfaces 11 and 12 are the object side glass surface and the image side glass surface of the plate glass 86. Radius of curvature and gap are in units of millimeters.

TABLE-US-00013 TABLE 7A Nd Vd Radius of (ref. (Abbe Surface Curvature Gap index) no.) 1 12.581 0.875 1.77250 49.6 2 3.598 2.342 3* 118.176 1.152 1.53461 56.0 4* 1.126 1.259 5* 2.437 1.368 1.58246 30.1 6* 5.274 0.673 7 infinity 0.420 8* 4.645 0.438 1.63494 24.0 9* 1.206 1.858 1.53461 56.0 10* 1.897 1.000 11 infinity 0.700 1.51680 64.2 12 infinity 1.219

[0239] Next, table 7B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 7B as well.

TABLE-US-00014 TABLE 7B 3rd surface 4th surface 5th surface 6th surface 8th surface 9th surface 10th surface K 0.00000E+00 1.13533E+00 4.01872E+00 0.00000E+00 5.79883E+00 4.07305E01 1.94772E01 A4 8.54655E04 1.39815E02 2.10044E02 1.45092E02 2.47392E02 1.81021E02 2.02986E02 A6 3.48800E06 3.24264E03 4.34476E03 3.69268E03 3.33467E03 7.87518E02 1.42584E03 A8 1.66300E06 2.03665E03 1.10311E03 3.93990E04 0.00000E+00 9.40828E03 4.08231E03 A10 1.82690E08 6.85755E04 1.91464E05 3.15360E05 0.00000E+00 1.13729E02 2.37074E03 A12 0.00000E+00 0.00000E+00 3.53083E06 0.00000E+00 0.00000E+00 4.88917E03 7.85272E04 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 1.01850E04 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0240] FIGS. 21A to 21D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 80. According to the imaging lens 80 of the present example, axial chromatic aberration is satisfactorily corrected as shown in FIG. 21A. Color bleeding is also suppressed as shown in FIG. 21B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 21A and 21B. Furthermore, according to the imaging lens 80 of the present example, field curvature is satisfactorily corrected as shown in FIG. 21C.

Reference Example 3

[0241] FIG. 22 is a configuration diagram (light ray diagram) of an imaging lens of Reference Example 3. An imaging lens 90 of the present example comprises, in order from an object side to an image side, a first lens 91 having negative power, a second lens 92 having negative power, a third lens 93 having positive power, and a fourth lens 94 having positive power, as shown in FIG. 22. A diaphragm 95 is disposed between the third lens 93 and the fourth lens 94, and plate glass 96 is disposed on the image side of the fourth lens 94. An image-forming surface 19 is in a separate position from the plate glass 96. The fourth lens 94 is a cemented lens comprising an object side lens 97 having negative power and an image side lens 98 having positive power. An image side lens surface 97b of the object side lens 97 and an object side lens surface 98a of the image side lens 98, which constitute cemented surfaces of the cemented lens, have the same shape. The object side lens 97 and the image side lens 98 are bonded by a resin adhesive, but there is essentially zero gap between the object side lens 97 and the image side lens 98.

[0242] When the F number of the imaging lens 90 of the present example is Fno, the half angle of view is , and the entire length of the lens system is L, these values are as follows.

[0243] Fno=2.0

[0244] =97.6

[0245] L=15.633 mm

[0246] When f is the focal point distance of the entire lens system, f1 is the focal point distance of the first lens 91, f2 is the focal point distance of the second lens 92, f3 is the focal point distance of the third lens 93, f4 is the focal point distance of the fourth lens 94, f41 is the focal point distance of the object side lens 97, and f42 is the focal point distance of the image side lens 98, these values are as follows.

[0247] f=1.149 mm

[0248] f1=8.499 mm

[0249] f2=2.585 mm

[0250] f3=3.991 mm

[0251] f4=3.208 mm

[0252] f41=3.508 mm

[0253] f42=1.833 mm

[0254] In the imaging lens 90 of the present example, when Sg1H is the amount of sag in the image side lens surface 97b of the object side lens 97 at height H in the effective diameter of the image side lens surface 97b of the object side lens 97 in a direction orthogonal to the optical axis L9, Sg2H is the amount of sag in the object side lens surface 98a of the image side lens 98 at height H, Rs is the radius of curvature of the image side lens surface 97b of the object side lens 97, R31 is the radius of curvature of the object side lens surface 93a of the third lens 93, and R32 is the radius of curvature of the image side lens surface 93b of the third lens 93, then the conditional expressions (2) and (4) to (6) given in the description of Example 1 are satisfied. The values of the conditional expressions (4) to (6) are as follows.

Sg1HSg2H(2)

0.9Rs/f=1.1101.3(4)

3.0(f41/f42)/f=1.671.5(5)

R31=3.342|R32|=|5.935|(6)

[0255] Furthermore, in the imaging lens 90 of the present example, the Abbe number of the first lens 91, the second lens 92, and the image side lens 98 is 40 or greater, and the Abbe number of the third lens 93 and the object side lens 97 is 31 or less, whereby chromatic aberration is corrected.

[0256] Next, table 8A shows lens data of the lens surfaces of the imaging lens 90. In table 8A, the lens surfaces are specified in order counting from the object side. Lens surfaces marked with an asterisk are aspheric. Surface 7 is the diaphragm 95, and surfaces 11 and 12 are the object side glass surface and the image side glass surface of the plate glass 96. Radius of curvature and gap are in units of millimeters.

TABLE-US-00015 TABLE 8A Radius of Nd (ref. Vd (Abbe Surface Curvature Gap index) no.) 1 16.292 1.000 1.77250 49.6 2 4.554 2.863 3* 52.037 1.359 1.53461 56.0 4* 1.432 1.602 5* 3.342 2.021 1.58246 30.1 6* 5.935 0.889 7 infinity 0.952 8* 3.437 0.500 1.63494 24.0 9* 1.275 1.790 1.53461 56.0 10* 2.164 1.000 11 infinity 0.600 1.51680 64.2 12 infinity 1.057

[0257] Next, table 8B shows aspheric coefficients for stipulating the aspheric shapes of the aspheric lens surfaces. The lens surfaces are specified in order counting from the object side in table 8B as well.

TABLE-US-00016 TABLE 8B 3rd surface 4th surface 5th surface 6th surface 8th surface 9th surface 10th surface K 3.33493E+01 1.29400E+00 4.40184E+00 0.00000E+00 1.49298E+00 5.08447E01 4.39594E01 A4 6.99972E04 9.34144E03 1.33728E02 1.33056E02 1.36471E02 6.31739E03 2.28238E02 A6 1.13834E05 6.88100E04 5.92956E04 2.58752E03 1.31356E03 1.87118E02 2.73430E03 A8 8.10438E07 1.84424E04 8.48007E05 9.16595E04 0.00000E+00 5.29138E03 1.36823E03 A10 2.53050E08 3.12281E05 1.84343E05 7.96107E05 0.00000E+00 4.63914E03 1.80092E04 A12 0.00000E+00 0.00000E+00 1.83298E06 0.00000E+00 0.00000E+00 1.03406E03 4.37716E05 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 1.66015E05 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00

[0258] FIGS. 23A to 23D are a longitudinal aberration graph, lateral aberration graphs, a field curvature graph, and a distortion aberration graph of the imaging lens 90. According to the imaging lens 90 of the present example, axial chromatic aberration is satisfactorily corrected as shown in FIG. 23A. Color bleeding is also suppressed as shown in FIG. 23B. Both axial chromatic aberration and magnification chromatic aberration are corrected in a balanced manner in the peripheral portions as well, as shown in FIGS. 23A and 23B. Furthermore, according to the imaging lens 90 of the present example, field curvature is satisfactorily corrected as shown in FIG. 23C.

SYMBOLS

[0259] 10, 20, 30, 40, 50 Imaging lenses [0260] 11, 21, 31, 41, 51 First lenses [0261] 12, 22, 32, 42, 52 Second lenses [0262] 13, 23, 33, 43, 53 Third lenses [0263] 14, 24, 34, 44, 54 Fourth lenses (cemented lenses) [0264] 17, 27, 37, 47, 57 Object side lenses [0265] 18, 28, 38, 48, 58 Image side lenses [0266] 15, 25, 35, 45, 55 Diaphragms [0267] B1, B2, B3, B4, B5 Resin adhesive layers [0268] L1, L2, L3, L4, L5 Optical axes [0269] I1, I2, I3, I4, I5 Image-forming surfaces [0270] 60 Imaging device [0271] 61 Image pick-up device [0272] 61a Sensor surface [0273] 62 Optical filter